The recent proliferation of devices employing wireless communication technologies has resulted in the inclusion of multiple systems in a single device. For example, Bluetooth and wireless local area network (WLAN) communication systems are often implemented in a single device. As will be discussed below, careful design must be employed to minimize conflicts and improve the quality of service.
Bluetooth is a short-range communication protocol and is often used to connect and exchange information between mobile phones, computers, digital cameras, wireless headsets, speakers, keyboards, mice or other input peripherals, and similar devices. Bluetooth allows for the creation of a personal area network (PAN) between a master and up to seven slaves and has an operating range of approximately ten meters. For many Bluetooth applications, it is necessary to ensure the uninterrupted delivery of correctly ordered data packets.
Similarly, WLAN systems may utilize any of the medium-range communication protocols in the IEEE 802.11 family of standards and are typically directed to larger networks. WLAN communications provide relatively high data rates over relatively long distances, offering an easy interface to existing network infrastructures. As such, the nature of a significant portion of WLAN traffic makes it less susceptible to packet order and delivery time problems.
Since Bluetooth and WLAN systems have different characteristics, it is often desirable to provide both functionalities. Despite the advantages of providing Bluetooth and WLAN functionalities in a single device, careful design is required to minimize interference and improve the quality of service. Although WLAN communications operate on an asynchronous protocol and access the wireless medium using a Carrier Sense Multiple Access/Collision Avoidance (CSMA/CA) mechanisms while Bluetooth communications rely on time division multiplex access (TDMA) mechanisms, both share the 2.4 GHz Industrial, Scientific and Medical Device band (ISM) band. As a result, interference between the two communications systems can occur.
This problem is exacerbated by the physical collocation of the systems if both are implemented in a single device. When the Bluetooth and WLAN devices are collocated, a signal transmitted from one device may saturate a low noise amplifier (LNA) in a receiver of the other device, then causing the receiver to be desensitized. For example, if the Bluetooth module is receiving a packet at the same time that the WLAN module is transmitting, then the transmit power of the WLAN module may spill into the receiver of the Bluetooth module and desensitize the receiver. The desensitization of the receiver may cause degradation in performance, loss of data, failure in communication, and/or other deleterious effects.
Collocation of these devices may entail using the same antenna, being located on the same circuit board or coupled circuit boards, being located on the same integrated circuit chip or coupled chip sets, being located within the same apparatus (e.g., a laptop computer or a mobile device), or any combination thereof. For example, a current trend is the move from each system being carried on separate integrated circuits to merging as many functions as possible onto a single integrated circuit in system on a chip (SOC) implementations. If the collocated devices are both operational, then there is an approximately 28% chance that a Bluetooth transmission will be sent on the frequency channel used by the WLAN device, causing interference with the WLAN transmission or vice versa.
To prevent such interference between collocated WLAN and Bluetooth systems, arbitration schemes are often employed to schedule transmissions to prevent or minimize simultaneous operation. Although arbitration can help minimize interference, there may be significant consequences to the operation of the affected systems. This is particularly true when the nature of the communications link involving one of the systems is associated with an enhanced priority. For example, to maintain sufficient quality for the transmission of voice traffic over Bluetooth, a synchronous connection-oriented (SCO) link may be employed. To guarantee adequate bandwidth, an SCO link reserves specific time slots that are dedicated to the SCO traffic. As a result, other wireless communication systems such as WLAN may be relegated to the unreserved time slots during SCO operation, which may prevent proper operation of WLAN.
Accordingly, what has been needed is a system and method for implementing WLAN and Bluetooth communications that minimizes interference. It would be desirable to provide systems and methods for maintaining the performance of one wireless communication system even while another wireless system is given priority. This invention accomplishes these and other goals.